Since the invention of the stereoscope in 1847, there has been a desire for emulating the 3-D images of nature instead of being content with two dimensional images which lack realism due to the absence of depth cues. Many techniques have been devised and developed for producing 3-D images, each varying in degree of success and quality of image. These techniques generally belong to two major classes, namely the autostereoscopic imaging class which produces 3-D images which can be viewed freely without spectacles, and the binocular stereoscopic imaging class which produces 3-D images which requires observers to wear spectacles or viewers. Techniques of the later class have been found in 3-D movies of the 1950's and in occasional 3-D image productions such as 3-D comic books.
Color separation of stereo images has been utilized for over fifty years in the production of photographs, 3D movies and the printed page. In prior art devices such as shown in U.S. Pat. No. 3,712,119, stereo images are separated by mutually extinguishing filters such as a blue-green lens filter over one eye and a red filter over the other eye. With this combination, a full true color image is not obtained, and this color combination may cause eye fatigue, and color suppression.
In the prior art an object of a single pure color matching the filter color e.g. red or blue-green, would be transmitted only to one eye and so would not appear in stereo. However, pure colors are rare, and most objects are off-white, or pastel shades and so contain all three primary colors. Thus, most objects will have some component of each color and this enables the separation of right and left stereo images.
Prints, drawings or representation that yield a 3-D image when viewed through appropriately colored lenses are called anaglyphs.
An anaglyph is a picture generally consisting of two distinctly colored, and preferably, complementary colored, prints or drawings. The complementary colors conventionally chosen for commercial printings of comic books and the like are orange and blue-green. Each of the complementary colored prints contains all elements of the picture. For example, if the picture consists of a car on a highway, then the anaglyph will be imprinted with an orange car and highway, and with a blue-green car and highway. For reasons explained below, some or all of the orange colored elements of the picture are horizontally shifted in varying amounts in the printing process relative to their corresponding blue-green elements.
An anaglyph is viewed through glasses or viewers having lenses tinted about the same colors used to prepare the anaglyph (hereinafter, "3-D glasses"). While orange and blue-green lenses are optimally used with an orange and blue-green anaglyph, red and blue lenses work satisfactorily in practice and apparently are conventionally used.
The orange elements in the picture are only seen through the blue lens, the red lens "washing out" the orange elements. For the same reason, the green-blue elements are only seen through the red lens. Hence, each eye sees only one of the two colored pictures. But because the different colored elements are horizontally shifted in varying amounts, the viewer's eyes must turn inward to properly view some elements, and turn outward to properly view others. Those elements for which the eyes turn inward, which is what the viewer does to observe a close object, are naturally perceived as close to the viewer. Elements for which the viewer's eyes turn outward are correspondingly perceived as distant. Specifically, if the blue lens covers the viewer's right eye, as is generally conventional, then any blue-green element shifted to the left of its corresponding orange element appears to the viewer as close. The element appears closer the greater the leftward shift. Conversely, as a green-blue element is shifted only slightly leftward, not at all, or even to the right of its corresponding red element, that element will appear increasingly more distant from the viewer.
In addition to horizontally shifting the element pairs relative to each other, some users of anaglyphy for comic books also vertically shift the element pairs a slight amount relative to each other. Those users believe that the slight vertical shift improves the 3-D effect.
Normally 3-D images appear monochromatic when viewed through 3-D glasses.
Three dimensional techniques are closely related to the psychology and physiology of an observer's cognitive processes. Subtle changes in selection of portions of the spectrum presented to each eye can result in significant changes in the observer's perception. Even when viewing the same 3-dimensional image through the same viewers, different observers may perceive a 3-dimensional image in different ways.
One problem common to most observers arises when viewing a pure red or pure blue region of a 3-dimensional image through red/blue 3-dimensional glasses. In such circumstances, one eye will perceive black and the other eye will perceive nothing. This has a psychological and/or physiological impact on the viewer which most viewers find disturbing.
Further, when observing 3-dimensional images in which the left and right images are captured using complementary filters, the images reproduced in the colors of the filters, and viewed through viewers of the same colors (e.g. red/blue glasses) which separate the images, 3-dimensional images appear only in black and white. That is, color information is lost in the preparation of the 3-dimensional image. This is characteristic of most 3-dimensional images.
When processing color images using computers, it is common to separate an image into (e.g.) red, green and blue image components. Commonly each color component is referred to as an image plane. In the display of color images on a color cathode ray tube it is common to apply information from each color image plane to a respective electron gun of the cathode ray tube.
Normally, in the past, when preparing 3-dimensional motion pictures, the anaglyph frames were prepared in the post production suite.
When color images are captured, it sometimes occurs that one of the colors utilized for representing the image may be overexposed or underexposed as reflected, inter alia, in an inadequate dynamic range for that color. That is, anytime the color appears at all, it appears at maximum value or anytime it appears it appears at some minimum value instead of being spread over the entire dynamic range of representation. This adversely affects the quality of 3-D image produced
The prior art generally required complex specialized equipment for the transmission of 3-dimensional images. This inhibited the use of 3-D technology because much capital investment has been devoted to equipment for handling regular 2-dimensional images. It would be desirable to utilize 2-dimensional transmission equipment to produce 3-dimensional images.